To write a number in scientific notation you must know:
1. A number in scientific notation is written as the product of a number (integer or decimal) and a power of 10
2. A number can be converted to scientific notation by increasing the power of 10 by one for each place the decimal point is shifted to the left.
Then so:
[tex]34000=3,4x10^3[/tex][tex]43000000=4.3x10^7[/tex][tex]0.0000087=8.7x10^{-6}[/tex][tex]91000000=9.1x10^7[/tex][tex]16.6x10^3=1.66x10^4[/tex][tex]0.00372x10^{-3}=3.72x10^{-6}[/tex]